The invention relates to cylinder ampoules having a first end sealed by a closure through which an injection unit can communicate with a medicament in the ampoule and a second end closed by a piston which can be forced into the ampoule to press out a dose of a medicament stored in the ampoule between the closure and the piston through said injection unit.
It shall be noticed that a cylinder is defined as a surface described when a line, the generatrix, with a defined orientation in space is moved along a guiding curve. What colloquially is called a cylinder is a so-called right circular cylinder, i.e. a cylinder whose guiding curve is a circle and whose generatrix is a line perpendicular to the plane of said circle. When talking about cylinder ampoules the word cylinder should be interpreted in the widest sense of the word although cylinder ampoules known so far are of the kind corresponding to the colloquial interpretation of the word cylinder.
Cylinder ampoules may be designed for use in syringes which are e.g. used by diabetics for the injection of insulin. Some insulin types are suspended in a liquid and the ampoule has to be shaken, rotated and turned upside down for some time to re-establish the suspension of the insulin crystals which will form a sediment when the ampoule is not in use. In a common cylinder ampoule having a circular cross-section perpendicular to its axis rotating of the ampoule will only result in a rotation of the ampoule and its content as a whole when the rotation of the ampoule is stopped, the liquid body will continue its rotation and the outer part of the rotating liquid body will break away some of the crystals which have segregated on the inner wall of the ampoule and suspend them in the said outer part of the rotating liquid body, but a homogeneous suspension where the concentration of crystals are equally suspended in the outer part and the part near the axis is difficult to obtain. Alternatively the ampoule may rotate without immediately drawing the liquid body with it. Also in this case a suspension of the segregated crystals in the outer part of the liquid body may be obtained when the ampoule wall moves relative to the liquid body but also in this case a homogeneous suspension is difficult to obtain.
From EP 235 691 it is known to place in the ampoule one or more mixing bodies in the shape of balls made from a material having a density which is different from the liquid. When the ampoule is rotated the balls will run along the wall and loosen crystals sediments. However, the balls may have a grinding effect on the crystals which may then be deactivated.